In recent years, development is underway on hybrid vehicles that combine an internal combustion engine with a motor-generator (hereinafter simply called “motor”) as a source of power. As a configuration of a hybrid drive device used in such a hybrid vehicle, what is called a parallel (one-motor stepped speed change) hybrid drive device is proposed that is structured to include a motor drivingly coupled to an input shaft (input member) drivingly coupled to an internal combustion engine and a stepped speed change mechanism that changes speed of rotation of the input shaft in a stepped manner (refer to Patent Document 1).
Patent Document 1 proposes to perform shift control in the parallel hybrid drive device having the stepped speed change mechanism so as to make the rotational speed of the input shaft coincide with a set target rotational speed while making the motor generate inertia torque of input-related members (members drivingly coupled to the input shaft) required during the shifting in the stepped speed change mechanism.